Traditional power generation, either in large or small scales, usually occurs in the forms of burning fossil fuels, such as coal, natural gas and petroleum. These methods typically cause environmental pollution. For example, an Internal Combustion Engine using the petroleum normally releases particulate matters, nitrogen oxides, carbon dioxide, sulfur monoxide and sulfur oxides into the air, which are toxic to human and animals. Although nuclear power plants generate about 13˜14% of the world's electricity at present, many organizations (e.g. Green Peace International) and individuals believe that nuclear power poses threats to people and environment. Alternative sources, including various forms of renewable energy, generally face the problem of high cost and poor efficiency. Technologies for power generation with high efficiency, less pollution and low cost are much desired.